Bubbles of air form a type of ground in the level; the bubbles move on their own. The player cannot leave them unless they are capable of surviving underwater. (Before NetHack 3.6.0, levitating or flying allowed the player to leave the bubbles, but this is no longer the case!) Water walking or freezing the water with a blast of cold will not work. The player arrives in a bubble on the left-hand side of the screen. The magic portal to the Astral Plane is located in another one of the bubbles (initially on the right-hand side of the screen) and travels around the map along with the bubble. Bubbles will continually merge and divide, so the player will eventually drift onto the portal through chance--although this can take many turns.

Randomly located around the level are nineteen water elementals, eight electric eels, eight giant eels, nine kraken, four sharks, four piranhas, four jellyfish, and four other random monsters.

The Plane of Water is ineligible to leave bones files. The entire level is no-teleport and has an undiggable floor. You cannot engrave on this level, even with wands. You cannot cast a targeted spell, i.e., cone of cold or fireball at skilled or higher.

Strategy

Unless you have magical breathing, or have genocided all sea monsters, there is more-than-usual danger of drowning while on this plane. Usually, it is enough to be very fast and unencumbered, as you can simply stay away from the eels. The usual precautions are recommended. A ring of conflict can help keep the sea monsters distracted. A bolt of cold down at the water will not rescue you from drowning.

Finding the magic portal can be difficult, because the portal moves along with its bubble. It is generally best to go to the center immediately and detect traps there. A confusedscroll of gold detection is the safest way, and a crystal ball works too (but is less safe). The portal might not be around when you reach its former location, but will still be revealed, and visible once you enter its bubble. In some cases, wearing the Amulet of Yendor might help find the portal.

Some players genocide sea monsters right after entering this level to empty it completely. (If sea monsters are already genocided when you enter, they will be replaced with random monsters.)